Hydrometallurgical treatment of copper-containing materials, such as copper ores, concentrates, and other copper-bearing materials, has been well established for many years. Currently, there exist many creative approaches to the hydrometallurgical treatment of these materials; however, common to almost all of the processes either now known or under development is the use of solvent/solution extraction and electrowinning (SX-EW) operations for solution purification and copper recovery.
The traditional hydrometallurgical process for copper recovery involves first leaching copper-containing material with sulfuric acid solution, either atmospherically or under conditions of elevated temperature and pressure. The resultant liquid stream—the so-called pregnant leach solution—is collected and processed in a solvent/solution extraction stage, in which the leach solution is mixed with an organic solvent (i.e., an extractant mixed with a suitable diluent, such as kerosene). The organic phase selectively removes the copper from the pregnant leach solution. The copper-loaded organic phase is then mixed with an aqueous acid solution, which strips the copper from the extractant, producing a solution stream suitable for electrowinning. This resultant solution is highly concentrated in copper, is relatively pure, and typically is processed in an electrowinning circuit to yield high quality copper cathode.
Purification of copper from the pregnant leach solution by solvent/solution extraction has proven to be a successful means of providing a concentrated copper solution suitable for electrowinning of highly pure copper metal. Direct electrowinning of copper—that is, plating of copper directly from the pregnant leach solution without the intervening step of purification by solvent/solution extraction—is known. However, the copper recovered by such so-called direct electrowinning processes often is too impure for sale or use as is, and thus, generally must be further refined at an additional cost, or may be sold at a discount. More specifically, prior art techniques have shown the ability for direct electrowinning of copper to produce a relatively low-quality copper product.
An effective and efficient method to recover copper from metal-bearing materials, such as, for example, chalcopyrite, chalcocite, bornite, covellite, digenite, and enargite, that enables high copper recovery to be achieved at a reduced cost over conventional processing techniques would be advantageous.